The invention relates to gas metal arc welding comparatively thick metal plates. More particularly, the invention relates to a multi-position method for welding thick abutting aluminum plates wherein welding can be effected on each surface of the plates in one pass in either the flat, vertical, horizontal or overhead welding position.
As used herein, "single pass" refers to welding one side of abutting plates in one pass. Because single pass welding offers many advantages over conventional multi-pass welding, those involved in the welding field have spent considerable time and effort developing single pass techniques and methods, particularly with respect to welding thick aluminum plates. Single pass welding, in addition to eliminating interpass weld defects (as there is only one pass), provides economic advantages such as lower gas consumption in shielding the weld and less welding time per weld (i.e., multi-pass techniques take more time and therefore are more costly).
While much progress has been made, there still remains a need for simpler and more economical single pass processes that can be employed in a variety of welding positions. Multi-position methods reduce costs since a single joint preparation can be used on most plates to be joined. For example, special joint preparation expenses, such as joint designs, typically required by methods only amenable to a few welding positions would be eliminated.
As used herein, "vertical welding" refers to welding vertically disposed plates which form a vertically extending weld line. "Horizontal welding" refers to welding vertically disposed plates forming a horizontally extending weld line. "Flat welding" refers to welding substantially horizontally disposed plates wherein the torch is positioned above the plates. "Overhead welding" refers to welding substantially horizontally disposed plates wherein the torch is positioned below the plates.
U.S. Pat. No. 4,038,514 to Ashton recognizes and discusses the advantages of single pass welding thick aluminum plates and discloses a method providing for such. However, Ashton's method is only amenable to welding vertically extending plates forming substantially vertical weld lines. The Ashton method also requires that a backhand torch angle be used.
In a previous patent issued to Walter Reichelt and Malcolm Hoy; namely, U.S. Pat. No. 4,292,496, there is disclosed a single pass method for welding plates in the horizontal and vertical positions. This method, however, is somewhat complicated in that the method requires that a welding groove be cut on one side surface of the abutting plates after the other side has already been welded.
Also relating to one pass butt welding is U.S. Pat. No. 2,916,600 to Tichler which discloses a single pass method for we1ding in the vertical position.
Another important aspect of welding thick aluminum plates is ease of joint preparation. A joint design that is difficult to prepare takes more time and is therefore more costly. Previously mentioned U.S. Pat. No. 4,038,514 to Ashton discloses the use of a double bevel joint geometry wherein the abutting edge surfaces of each plate are beveled to form two V-shaped grooves, one on each plate surface, with a land surface therebetween. Other joint geometries commonly employed for butt joint welding are described on pages 8.3 through 8.8 of the Welding Handbook, 6th Edition, American Welding Society.
While many of the problems associated with welding thick aluminum plates have been resolved, there still remains a need for a gas metal arc welding method that is easily operated (for example, by using a forehand as opposed to a backhand lead angle), requires minimal joint preparation, is capable of depositing a weld bead on the surface of a relatively thick aluminum or aluminum alloy plate in a single weld pass, and is amenable to welding in a variety of positions.